class_docstr: A class to open and interact with fits files from SDSS
  
  Parameters
  ----------
  buf : string or file buffer (optional)
      file path, buffer, or url of SDSS spectra fits file
      if None, then initialize an empty instance.
  
  Notes
  -----
  This class only provides access to a subset of the information available
  in the sdss spectra fits file.  The raw fits data can be accessed using
  the fits object directly.  This can be found in the attribute
  ``hdulist``.  For details, please refer to the data description:
  http://www.sdss.org/dr7/dm/flatFiles/spSpec.html
docstr: return a mask showing where noise spikes to frac over the local
  background
docstr_tok: ["return","a","mask","showing","where","noise","spikes","to","frac","over","the","local","background"]
code: def compute_mask(self, frac=0.5, filtwidth=5):
      """
      return a mask showing where noise spikes to frac over the local
      background
      """
      smoothed_noise = gaussian_filter1d(self.error, filtwidth)
      mask = (
          (self.error >= (1 + frac) * smoothed_noise)
          | (self.error <= 0)
          | (self.error >= self.large_err)
          | (self.spectrum == 0)
      )
      mask_filtered = uniform_filter1d(
          mask.astype(float), max(3, filtwidth)
      )
      return mask_filtered > 0.5 / filtwidth
  
imports: import gc
  import numpy
  from scipy.ndimage import gaussian_filter1d, uniform_filter1d
  from scipy import interpolate
  from .None import download_with_progress_bar
label_desc: Use image node_id 16 for calling the SDSSfits obj's underlying member method code with example usage: obj.compute_mask(frac, filtwidth) and returns: unknown